JP3280399B2 - Electrodeless lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge gas by applying a high-frequency magnetic field to the discharge gas from outside the bulb without having electrodes inside the bulb made of a light-transmitting material filled with the discharge gas. The present invention relates to an electrodeless discharge lamp that emits excited light.

[0002]

2. Description of the Related Art Conventionally, an electrodeless discharge lamp has been known in which a high-frequency magnetic field acts on a discharge gas sealed in a bulb to excite the discharge gas to emit light. This kind of electrodeless discharge lamp is small, high power,
Since it has features such as a long life, research and development have been conducted in various places, and various uses as a high-output point light source and the like have been considered.

As shown in FIG. 4, an electrodeless discharge lamp is provided with a bulb-shaped bulb 1 surrounding an induction coil 2, and a high-frequency current is applied to the induction coil 2 to be enclosed in the bulb 1. There is one in which a high-frequency magnetic field is applied to the discharged discharge gas to excite the discharge gas to emit light (Japanese Patent Laid-Open No. 57-78766). As the discharge gas, a gas containing mercury vapor is used, and emits light by excitation of the mercury vapor.

By the way, the magnetic field formed around the air-core coil used as the induction coil 2 is strongest inside the induction coil 2, but in the above configuration, the high-frequency magnetic field inside the induction coil 2 is changed to the discharge gas. Therefore, there is a problem that the efficiency is low. On the other hand, as shown in FIG.
An induction coil 2 having a winding wound around the outer periphery of the valve 1;
An electrodeless discharge lamp in which a high-frequency current flows from the high-frequency power supply 4 to the induction coil 2 has been considered. In this configuration, since a high-frequency magnetic field is applied to the discharge gas inside the induction coil 2, the efficiency is higher as compared with the configuration in FIG.

As a discharge gas of these electrodeless discharge lamps, a mixed gas of a luminescent substance such as mercury vapor and a rare gas is generally used. When a discharge gas containing a luminescent substance is used, there is a problem that initial startup is relatively easy, but restart is difficult. Further, when the temperature rises (especially during lighting), since the vapor pressure of the luminescent substance changes exponentially, it is difficult to match with a high-frequency power supply for supplying a high-frequency current to the induction coil 2 and the matching cannot be achieved. And a problem of disappearing. On the other hand, if the discharge gas does not include a luminescent substance, the alignment becomes easier, but the initial startup becomes difficult. If a high voltage is applied to the induction coil,
Although it is possible to start forcibly, a high-frequency power supply capable of outputting a high voltage is required, which causes a problem that the high-frequency power supply as a lighting circuit becomes large. That is, an electrodeless discharge lamp including an electrodeless discharge lamp and a high-frequency power supply is increased in size.

In order to solve the above-mentioned problem, as shown in FIG. 6, a winding of an induction coil 2 is wound around the outer periphery of a bulb 1 to make a high-frequency magnetic field act on a discharge gas efficiently. By disposing a pair of auxiliary electrodes 3 facing each other on both sides of the bulb 1 in the axial direction of the induction coil 2, an electrodeless discharge lamp that is relatively easy to start even with a discharge gas containing no luminescent substance is provided. It has been proposed (U.S. Pat. No. 4,894,589, U.S. Pat. No. 4,902,937). In this electrodeless discharge lamp,
Prior to the application of the high-frequency current to the induction coil 2, a high-frequency voltage is applied between the auxiliary electrodes 3 so that the preliminary discharge is performed, and the high-frequency current is applied to the induction coil 2 when the preliminary discharge occurs. By doing so, it is intended to facilitate starting.

[0007]

When the induction coil 2 is lit by supplying a high-frequency current to the induction coil 2, a rotating electric field is generated in the bulb 1 by the high-frequency magnetic field. Is what runs. Since the rotating electric field is generated in a plane orthogonal to the magnetic flux, at the time of lighting, the discharge plasma runs along the winding direction of the winding of the induction coil 2. On the other hand, the preliminary discharge generated between the auxiliary electrodes 3 is generated in a direction orthogonal to the rotating electric field, and both ends are restricted by the auxiliary electrodes 3. There is a problem that relatively large energy is required in order to shift to a state in which the discharge plasma runs along. That is, even if the pair of auxiliary electrodes 3 are provided, there is a problem that starting is not so easy.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrodeless discharge lamp which is easy to start and does not require a large high-frequency power source and which can be formed relatively compactly. It is.

[0009]

According to the first aspect of the present invention, in order to achieve the above object, the first induction coil is formed by winding a coil around an outer periphery of a bulb made of a light transmitting material in which a discharge gas is sealed. In an electrodeless discharge lamp, a high-frequency current is supplied from a high-frequency power source, and a high-frequency magnetic field is applied to the discharge gas sealed in the bulb to excite and emit the discharge gas.
A single-pole auxiliary electrode, to which a high-frequency voltage is applied from the second high-frequency power supply to generate a string-shaped preliminary discharge in the bulb, is electrostatically coupled to a space in the bulb near the outer wall surface of the bulb. The first high-frequency power supply and the second high-frequency power supply are provided separately from each other, and the second high-frequency power supply is configured such that the amplitude value of the voltage applied to the auxiliary electrode with respect to the ground is sufficiently large. The output voltage is set and the
Output a parallel resonant circuit in which the inductor and capacitor are connected in parallel
Provided as a circuit, the inductance component of the inductor is sufficient
That is, the constant of the parallel resonance circuit is set so as to increase in minutes .

According to the second aspect of the present invention, the output frequency of the second high frequency power supply is set higher than that of the first high frequency power supply.

[0011]

According to the first aspect of the present invention, a single-pole auxiliary electrode capable of generating a string-like preliminary discharge in the bulb by applying a high-frequency voltage is provided near the outer wall surface of the bulb and in the bulb. Since it is provided at a position where it is electrostatically coupled to the space, a preliminary discharge can be generated by the auxiliary electrode before the high-frequency current is applied to the induction coil to excite and discharge the discharge gas. Even if it is not included, it can be easily started. Also,
Since the auxiliary electrode is monopolar, one end of the preliminary discharge is constrained by the auxiliary electrode but the other end is a free end, and the direction in which the discharge plasma generated by the high-frequency magnetic field generated around the induction coil runs. Even if the direction of the preliminary discharge is different, it is easy to shift the preliminary discharge to the direction in which the discharge plasma runs at the time of lighting. The energy required for this is reduced. Further, the first high-frequency power supply and the second high-frequency power supply are separately provided, and the output voltage of the second high-frequency power supply is set so that the amplitude value of the voltage applied to the auxiliary electrode with respect to the ground is sufficiently large. Therefore, it is easy to design each high-frequency power supply, apply a high-frequency voltage to the auxiliary electrode sufficient to generate a preliminary discharge, and apply a high-frequency current to the induction coil sufficient to generate an arc discharge. You can. Here, the preliminary discharge includes
Since a relatively high voltage is required, the output voltage of the second high-frequency power supply is set so that the amplitude value with respect to the ground becomes sufficiently large.

Moreover, the second high-frequency power supply is an inductor.
Output circuit is a parallel resonant circuit in which a capacitor and a capacitor are connected in parallel.
As an output circuit of the second high-frequency power supply so that the inductance component of the inductor becomes sufficiently large .
Since the constant of the parallel resonance circuit is set, the voltage between both ends of the parallel resonance circuit becomes high, and a sufficiently high voltage can be applied to the auxiliary electrode, so that the preliminary discharge is easily generated, and as a result, the starting is started. The quality is improved. According to the configuration of claim 2 , the output frequency of the second high-frequency power supply is set higher than the output frequency of the first high-frequency power supply.
The impedance between the auxiliary electrode and the discharge gas in the bulb is reduced, and the preliminary discharge is likely to occur,
Startability is improved.

[0013]

(Embodiment 1) As shown in FIG. 1, the bulb 1 is formed in a spherical shape with a translucent material such as quartz glass, and is filled with xenon gas as a discharge gas at 100 Torr. The induction coil 2 is formed in a form in which a winding is wound around the outer circumference of a cylinder virtually set to enclose the valve 1. Here, the induction coil 2 is wound three turns, but the number of turns is not particularly limited, and it is sufficient that the induction coil 2 is wound one or more turns. A monopolar auxiliary electrode 3 is arranged near the outer wall surface of the bulb 1.
The auxiliary electrode 3 is, for example, 10 m on a side by a metal foil.
m square (ie, depending on the conductive material
Formed in a foil shape), and is attached to or close to the outer wall surface of the bulb 1. In the present embodiment, the position of the auxiliary electrode 3 is set at one end in the axial direction of the cylinder virtually set with respect to the induction coil 2, but is not limited to this.

The induction coil 2 is supplied with a high-frequency current from the first high-frequency power supply 4a to generate a high-frequency magnetic field. The high-frequency magnetic field acts on the discharge gas inside the bulb 1, thereby exciting the discharge gas and emitting light. It is supposed to. Further, a rotating electric field is generated in the bulb 1 by the high frequency magnetic field, and the discharge plasma generated in the bulb 1 by the rotating electric field rotates in the bulb 1. A high-frequency voltage is applied to the auxiliary electrode 3 from the second high-frequency power supply 4b via a connection line, and a high-frequency electric field generated around the auxiliary electrode 3 causes a string-like preliminary discharge to occur in the bulb 1. It has become. That is, the electrons accelerated by the high-frequency electric field generated around the auxiliary electrode 3 collide with the atoms of the discharge gas to ionize them, thereby generating a preliminary discharge. In such a preliminary discharge, one end is restricted by the auxiliary electrode 3 because the auxiliary electrode 3 is monopolar, but the other end is a free end and can move relatively freely. Here, the first high-frequency power supply 4
a and the second high-frequency power supply 4b include a high-frequency oscillator for obtaining a high-frequency output, an amplifier for power-amplifying the high-frequency output, a matching unit for matching the impedance with the induction coil 2 and the auxiliary electrode 3, and the like. Also, the second high-frequency power supply 4b
Are adapted to apply a high-frequency voltage between the auxiliary electrode 3 and the ground. The second high-frequency power supply 4b is connected to the oscillation unit AC
Is applied to the auxiliary electrode 3 through an output circuit composed of a parallel resonance circuit in which an inductor L and a capacitor C are connected in parallel. Here, the resonance frequency f of the parallel resonance circuit is f = １ ／ π by the inductor L and the capacitor C.
(LC) ^1/2, and the voltage across inductor L is infinite in an ideal resonance state, but the voltage across inductor L is actually the inductance of inductor L due to the presence of a resistance component. Will be determined by FIG. 2 shows the relationship between the inductance when inputting 20 W to the auxiliary electrode 3 and the voltage across the inductor L. As is clear from FIG. 2, the voltage across the inductor L can be increased as the inductance increases. On the other hand, as the high-frequency voltage applied to the auxiliary electrode 3 is higher with respect to the ground, the preliminary discharge is more easily generated. Therefore, the inductance of the inductor L constituting the parallel resonance circuit is made sufficiently large, so that the preliminary discharge is easily generated. Thus, the constant between the inductor L and the capacitor C is determined. FIG. 3 shows the relationship between the inductance of the inductor L and the minimum starting input power to the induction coil 2. As is clear from FIG. 3, it can be seen that the minimum starting input power to the induction coil 2 decreases as the inductance increases.

To turn on the electrodeless discharge lamp configured as described above, first, a high-frequency voltage is applied to the auxiliary electrode 3 to generate a preliminary discharge. The preliminary discharge gradually extends from the auxiliary electrode 3 and reaches almost the opposite side of the bulb 1. Here, when a high-frequency current is applied to the induction coil 2, the free end of the preliminary discharge is induced along the rotating electric field generated by the high-frequency magnetic field generated around the induction coil 2, and a loop-shaped discharge path is formed. Thereafter, when the loop is connected, the discharge gas shifts to arc discharge to generate a discharge plasma, and the discharge gas is excited to generate a strong light emission to be turned on. After the transition to the lighting state, the application of the high-frequency voltage to the auxiliary electrode 3 becomes unnecessary. Here, the high-frequency current to the induction coil 2 is given after the preliminary discharge has occurred, but at the same time that the high-frequency voltage is applied to the auxiliary electrode 3, the high-frequency current is applied to the induction coil 2 to perform the preliminary discharge. May occur, the high-frequency current to the induction coil 2 may be increased.

As described above, the preliminary discharge can be generated by applying the high-frequency voltage to the auxiliary electrode 3, so that the transition to the arc discharge is facilitated and the starting is facilitated. That is, as compared with the case where there is no preliminary discharge, the initial input to the induction coil 2 is greatly reduced, and the startability is improved. Further, a second high-frequency power supply 4b serving as a power supply for the auxiliary electrode 3 is
By providing the power supply for the induction coil 2 separately from the first high-frequency power supply 4a, the design of each power supply is facilitated, and a high-frequency voltage sufficient to cause a preliminary discharge is applied to the auxiliary electrode 3. Thus, a high frequency current sufficient to cause arc discharge can be supplied to the induction coil 2.

Here, xenon gas is used as the discharge gas.
Instead, another single gas or a mixed gas may be used. Ma
In particular, regarding the position, size, and shape of the auxiliary electrode,
Not limited.  Example 2 In this example, a rare gas was used as a discharge gas and a luminescent material was used.
Using a mixture of all metals and metal halides
You. Metals and metal halides can be used alone or in mixtures.
Is also good. For example, NaI-TaI-InI etc.
Mix.

When a discharge gas mixed with such a luminescent material is used, excitation light emission of a rare gas is generated immediately after transition to arc discharge, and white light is generated when the rare gas is xenon. Become. Thereafter, the vapor pressure of the luminescent substance increases, and a luminescent color is generated by the luminescent substance. As described above, high emission luminance can be obtained from the initial state, and a high-intensity electrodeless discharge lamp with good startup can be provided. Except for the components of the discharge gas, the configuration is the same as that of the first embodiment.

(Embodiment 3) In this embodiment, the output frequency of the second high-frequency power supply 4b is set higher than the output frequency of the first high-frequency power supply 4a. As the output frequency becomes higher, the impedance between the discharge gas in the bulb 1 and the auxiliary electrode 3 becomes smaller, the electrical coupling state becomes denser, and the preliminary discharge is more likely to occur. Here, if the frequency of the high-frequency current supplied to the induction coil 2 is increased, the impedance of the induction coil 2 is increased and the current becomes difficult to flow, and the required power cannot be supplied. The frequency cannot be set too high. Therefore, the output frequency of the first high-frequency power supply 4a is the same as the conventional one, and the output frequency of the second high-frequency power supply 4b is set high. The configuration of the present embodiment can be applied to both the first embodiment and the second embodiment.

(Embodiment 4) In this embodiment, although not shown, an auxiliary means for facilitating preliminary discharge is provided in addition to the auxiliary electrode 3, and a high-voltage generator comprising a piezoelectric element or the like is provided. Is used as an auxiliary means by disposing it close to the valve 1. In this configuration, when a high-frequency voltage is applied to the auxiliary electrode 3, a high voltage is generated in the vicinity of the bulb 1 by the auxiliary means, so that an ionization state necessary for generating a preliminary discharge in the bulb 1 is easily generated. That is, the pre-discharge is more likely to occur, so that the startability is further improved. The configuration of the present embodiment is effective when starting is difficult even if the auxiliary electrode 3 is provided, and is applicable to any of the configurations of the first to third embodiments.

[0021]

According to the first aspect of the present invention, a single-pole auxiliary electrode capable of generating a string-like preliminary discharge in the bulb by applying a high-frequency voltage is provided near the outer wall surface of the bulb. Since it is provided at a position where it is electrostatically coupled to the space inside, the auxiliary electrode can generate a preliminary discharge before the high-frequency current is applied to the induction coil to excite and discharge the discharge gas. Even when no luminescent substance is contained, an effect of easily starting can be obtained. In addition, since the auxiliary electrode is monopolar, the preliminary discharge has one end constrained by the auxiliary electrode but the other end free, and discharge plasma generated by a high-frequency magnetic field generated around the induction coil runs. Even if the direction is different from the direction in which the preliminary discharge occurs, it is easy to shift the preliminary discharge to the direction in which the discharge plasma runs at the time of lighting, compared to a case where a pair of auxiliary electrodes are arranged to face each other. This has the advantage that the energy required for starting is reduced. Further, the first high-frequency power supply and the second high-frequency power supply are separately provided, and the output voltage of the second high-frequency power supply is set so that the amplitude value of the voltage applied to the auxiliary electrode with respect to the ground is sufficiently large. So that the design of each high-frequency power supply is easy,
There is an effect that a high-frequency voltage sufficient to generate a preliminary discharge can be applied to the auxiliary electrode, and a high-frequency current sufficient to generate an arc discharge can be supplied to the induction coil.

Further , the second high-frequency power supply is an inductor.
Output circuit is a parallel resonant circuit in which a capacitor and a capacitor are connected in parallel.
As an output circuit of the second high-frequency power supply so that the inductance component of the inductor becomes sufficiently large .
Since the constant of the parallel resonance circuit is set, the voltage between both ends of the parallel resonance circuit becomes high, and a sufficiently high voltage can be applied to the auxiliary electrode, so that the preliminary discharge is easily generated, and as a result, the starting is started. The performance is improved. According to the configuration of claim 2 , since the output frequency of the second high-frequency power supply is set higher than the output frequency of the first high-frequency power supply, the impedance between the auxiliary electrode and the discharge gas in the bulb is reduced. As a result, the pre-discharge is likely to occur, and the startability is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment.

FIG. 2 is a diagram illustrating the principle of an embodiment.

FIG. 3 is a diagram illustrating the principle of the embodiment.

FIG. 4 is a sectional view showing a conventional electrodeless discharge lamp.

FIG. 5 is a configuration diagram using another conventional electrodeless discharge lamp.

FIG. 6 is a sectional view showing still another conventional electrodeless discharge lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve 2 Induction coil 3 Auxiliary electrode 4a 1st high frequency power supply 4b 2nd high frequency power supply L Inductor C Capacitor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-161361 (JP, A) JP-A-4-229598 (JP, A) JP-A-1-159356 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) H05B 41/24 H01J 61/54

Claims (2)

(57) [Claims] 1. A high-frequency current is applied from a first high-frequency power supply to an induction coil having a winding wound around the outer periphery of a bulb made of a light-transmitting material in which a discharge gas is sealed, and a discharge gas sealed in the bulb is supplied to the induction coil. In a non-electrode discharge lamp that excites and emits a discharge gas by applying a high-frequency magnetic field, a high-frequency voltage is applied from a second high-frequency power supply to generate a string-shaped preliminary discharge in the bulb. But,
The first high-frequency power supply and the second high-frequency power supply are provided separately near the outer wall surface of the valve and electrostatically coupled to the space inside the valve, and the second high-frequency power supply is
The output voltage is set so that the amplitude value of the voltage applied to the auxiliary electrode with respect to the ground is sufficiently large , and the inductor and the capacitor are connected.
A parallel resonant circuit connected in parallel with a capacitor is used as the output circuit.
The inductance component of the inductor is sufficiently large
An electrodeless discharge lamp characterized in that a constant of a parallel resonance circuit is set as follows . 2. The high-frequency power source according to claim 1, wherein the second high-frequency power source is a first high-frequency power source.
The electrodeless discharge lamp according to claim 1, wherein the output frequency is set higher than that of the discharge lamp .